Shao Linxiang, Bao Xiue, Li Zhaoying, Xing Chaoran, Crupi Giovanni, Gugliandolo Giovanni, Latino Mariangela, Si Liming, Sun Houjun, Wen Lianggong
School of Integrated Circuits and Electronics, Beijing Institute of Technology, 100081 Beijing, China.
Tangshan Research Institute of BIT, 063000 Tangshan, China.
Phys Chem Chem Phys. 2025 Jul 23;27(29):15584-15593. doi: 10.1039/d5cp00933b.
Two novel microwave sensors integrated with microfluidic techniques are introduced and experimentally validated, intended for testing magnetic bead solutions. The first is a transmission line sensor that operates over a wide frequency range from 1 GHz to 110 GHz, utilizing an easily integrable coplanar waveguide (CPW) structure. The second sensor is based on resonant principles and operates at approximately 25 GHz, composed of a CPW structure and a spiral-shaped defect ground structure (DGS). By selecting this frequency band, the minimum size of the DGS sensing area is restricted to 296 μm, about 0.025, which greatly reduces the volume of liquid samples needed. The transmission parameters of both sensors are analyzed using air, deionized (DI) water/ethanol solution, and magnetic bead solution as materials under test (MUTs). Micro-nano fabrication and on-chip measurements are conducted to validate the proposed sensors. Experimental results for the transmission line sensor demonstrate that the variation in || can be used as a parameter to detect magnetic beads in solutions across a wide frequency range. For the resonance sensor, the measurements show that an increase in the real part of the complex relative permeability results in a redshift of the resonance frequency, whereas an increase in the imaginary part reduces the quality factor. These effects are consistent with those observed for complex permittivity. However, a notable difference is that an increase in the real part of permeability also causes a slight decrease in ||, which aids in signal detection. In addition to the proposed sensors, a terahertz (THz) spectroscopy transmission method is also experimentally employed to investigate the permittivity of different types and concentrations of magnetic bead solutions. Our study offers a new perspective for enhancing detection sensitivity in microwave microfluidic biosensors by co-utilizing permittivity and permeability. This approach shows great promise for applications in cell sorting and precise measurement of bioliquids.
介绍了两种集成微流控技术的新型微波传感器，并进行了实验验证，旨在测试磁珠溶液。第一种是传输线传感器，工作频率范围为1GHz至110GHz，采用易于集成的共面波导（CPW）结构。第二种传感器基于谐振原理，工作频率约为25GHz，由CPW结构和螺旋形缺陷接地结构（DGS）组成。通过选择该频段，DGS传感区域的最小尺寸限制为296μm，约为0.025，这大大减少了所需液体样品的体积。使用空气、去离子（DI）水/乙醇溶液和磁珠溶液作为被测材料（MUT）分析了两种传感器的传输参数。进行了微纳制造和片上测量以验证所提出的传感器。传输线传感器的实验结果表明，||的变化可作为在宽频率范围内检测溶液中磁珠的参数。对于谐振传感器，测量结果表明，复相对磁导率实部的增加导致谐振频率红移，而虚部的增加会降低品质因数。这些效应与复介电常数观察到的效应一致。然而，一个显著的差异是磁导率实部的增加也会导致||略有下降，这有助于信号检测。除了所提出传感器外，还通过实验采用太赫兹（THz）光谱传输方法来研究不同类型和浓度磁珠溶液的介电常数。我们的研究通过共同利用介电常数和磁导率，为提高微波微流控生物传感器的检测灵敏度提供了新的视角。这种方法在细胞分选和生物液体精确测量应用中显示出巨大潜力。
